testing dark matter with neutrino detectors

Sergio Palomares-Ruiz

June 4, 2008

Testing Dark Matter

with neutrino detectors

Melbourne Neutrino Theory Workshop

Melbourne (Australia) June 2-4, 2008


June 4, 2008 Evidences of DM• Rotation curves of galaxies and

clusters

• Weak modulation of strong lensing, Oort discrepancy, weak gravitational lensing, velocity dispersions of dwarf spheroidal galaxies and of spiral gallaxy satellites…

Need non-luminous matter

Black-holes, brown dwarfs, white dwarfs, giant planets, neutron stars …?


June 4, 2008

Cosmological evidences

• WMAP Best-fit for a flat ¤CDM model:

mh2 = 0.1326 ± 0.0063

But… bh2 = 0.02229 ± 0.00073

Non-baryonic Dark Matter

B. D. Fields and S. Sarkar, PDG NASA / WMPA Science Team, WMAP 5-year results


June 4, 2008

Nature of the Dark Matter

Standard Model Neutrinos, sterile neutrinos, axions, neutralinos, sneutrinos, gravitinos, axinos, light scalars, from little Higgs models, Kaluza-Klein, super-heavy particles, Q-balls, mirror particles, charged massive particles, self-interacting particles, D-matter, cryptons, superweakly interacting particles, brane world particles, heavy fourth generation neutrinos…


June 4, 2008

What do we know about Dark Matter?

• Astrophysicist view:

• Particle Physicist view:


June 4, 2008 Detecting DM• Direct Detection

– Nuclear recoil produced by DM elastic scattering

• Collider Searches – Missing energy

• Indirect Detection– Observation of annihilation products

• Gamma-ray telescopes (MAGIC, CANGAROO-III, HESS, VERITAS, EGRET, GLAST…)

• Anti-matter experiments (HEAT, BESS, PAMELA…)

• Neutrino detectors/telescopes (IceCUBE, ANTARES, AMANDA, Super-Kamiokande…)


June 4, 2008 Direct Detection

D. S. Akerib et al. [CDMS Collaboration], Phys. Rev. D73:011102, 2006

G. Angloher et al. [CRESST Collaboration], Astropart. Phys. 23:325, 2005

Spin-independent Spin-dependent

Z. Ahmed et al. [CDMS Collaboration], arXiv:0802.3530

J. Angle et al. [XENON Collaboration],

Phys. Rev. Lett. 100:021303, 2008

H. S. Lee et al. [KIMS Collaboration], Phys. Rev. Lett. 99:091301, 2007

E. Behnke et al. [COUPP Collaboration], Science 319:933, 2008


June 4, 2008 Some DM properties• DM may acumulate in celestial bodies like the Sun• DM-nucleon elastic cross section sets the

normalization • Different annihilation channels imply different ν

flux

• How big is the annihilation cross section? • For a thermal relic: <σv> ~ 3 x 10-26 cm3/s• But…DM might only exist in the late Universe • <σv> sets the rate of DM annihilation in DM halos

• If DM is unstable, how long does it live?• τ would set the rate of DM decay in DM halos

Can we test them with neutrino detectors?


June 4, 2008


June 4, 2008

Indirect Neutrino Detection

• WIMPs elastically scatter with the nuclei of celestial bodies to a velocity smaller than the escape velocity, so they remain trapped inside

• Additional scatterings give rise to an isothermal distribution

• Trapped WIMPs can annihilate into SM particles

• After some time, annihilation and capture rates equilibrate

• Only neutrinos can escape

2

2

3

3124 GeV 50

pb 10

km/s 270

GeV/cm 3.0109

DMlocal

local

mvsC

eq

ann t

tC 2tanh

2

1


June 4, 2008Neutrinos from WIMP

annihilations

i

ii

ann

dE

dNBR

RdtdEd

dN

24

Distance source-detector

Branching ratio into annihilation channel i

Neutrino spectrum from annihilation channel i


June 4, 2008

Neutrino spectra at detection

Need to take into account oscillations and solar absorption

M. Cirelli et al., Nucl. Phys. B727:99, 2005


June 4, 2008 IceCube, ANTARES…

Counting experiments above some energy threshold

Detection of muon events induced by muon neutrinos


June 4, 2008 Limits from SK

S. Desai et al., Phys. Rev. D70:083523, 2004

Spin-independent Spin-dependent


June 4, 2008

Rates in a Neutrino Telescope

F. Halzen and D. Hooper, Phys. Rev. D73:123507, 2006

To get the same rate: trade annihilation channel by cross section


June 4, 2008

Future Neutrino Detectors

• Magnetized Iron Calorimeters– MINOS-like, INO…

• Totally Active Scintillator Detectors– NOvA, MINERvA…

• Liquid Argon Time Projection Chamber– GLACIER…

Very good angular and energy resolution for νe and/or ν¹ for 10’s of GeV →

suitable for low mass WIMPs

“Small” detectors: only suitable for neutrinos from annihilations in the Sun


June 4, 2008Angular and Energy Resolutions for MIND

• We take 5 GeV-energy bins

• We take the rms spread in the direction between the neutrino and the lepton:

E

GeVrms ~

T. Abe et al., The ISS Detector Working Group


June 4, 2008 Neutrino Events

ν¹-events νe-events

Determination of WIMP mass


June 4, 2008

O. Mena, SPR and S. Pascoli, Phys. Lett. B664:92, 2008

mDM = 50 GeVBR¿+¿- (hard) = 20%

mDM = 70 GeVBR¿+¿-(hard) = 10%


June 4, 2008


June 4, 2008

Model-independent bound

• Neutrinos are the least detectable particles of the SM

• From the detection point of view the most conservative assumption (the worst case) is that DM annihilates only into ν’s: Â Â → νν

• This is not an assumption about realistic models

• It provides a bound on the total annihilation cross section and not on the partial cross section to neutrinos

• Anything else would produce photons, and hence would lead to a stronger limit

J. F. Beacom, N. F. Bell and G. D. Mack, Phys. Rev. Lett. 99:231301, 2007


June 4, 2008 Strategy• Calculate neutrino flux: proportional

to annihilation cross section and ½DM2

• For E ~ 100 MeV – 100 TeV the main background: atmospheric neutrino flux

• Consider angle-averaged flux in wide energy bins

• Compare potential signal with the well known and measured background: set upper bound on the DM annihilation cross section


June 4, 2008 Signal

annsc JR

dE

dN

mdE

d

202

2

4

Experiment Particle Physics Astrophysics


June 4, 2008 Field of View

Neutrino Spectrum: Flavor democracy

Average of the Line of Sight Integration of ½2

cos12

mEdE

dN

3

2

cos 2)(11 1

cos 0

220

max

ddrR

Jsc

ann

22 cos2 scsc RRr cossin 222max scschalo RRR


June 4, 2008

Energy resolution: ¢log E = 0.34

GeV 10

GeV 1030 E

Eo

GeV 10 30 Eo

H. Yüksel, S. Horiuchi, J. F. Beacom and S. Ando, Phys. Rev. D76:123506, 2007

Other related limitsM. Kachelriess and P. D. Serpico, Phys. Rev. D76:063516, 2007N. F. Bell, J. B. Dent, T. D. Jacques and T. J. Weiler, arXiv:0805.3423J. B. Dent, R. J. Scherrer and T. J. Weiler, arXiv:0806.0370G. D. Mack, T. D. Jacques, J. F. Beacom, N. F. Bell and H. Yüksel, arXiv:0803.0157


June 4, 2008

Can we do better?

• Careful treatment of energy resolution and backgrounds: eg. limits on MeV DM

• We use SK data for E = 18-82 MeV

• Detection: νe + p → e+ + n

• Two main backgrounds: – Invisible muons– Atmospheric neutrinos

M. S. Malek, Ph.D thesisM. S. Malek et al., Phys. Rev. Lett. 90:061101, 2003


June 4, 2008

We perform a similar Â2 analysis as that done by SK to limit the flux of DSNB and we set an upper bound on the DM annihilation cross section

SPR and S. Pascoli, Phys. Rev. D77, 025025 (2008)SPR, arXiv:0805.3367


June 4, 2008

LENA: 50000 m3 scintillator after 10 years

Reactor BG DSNB Atmospheric BGSPR and S. Pascoli, Phys. Rev. D77, 025025 (2008)

What if this is actually the case and DM only annihilates into neutrinos?

C. Boehm, Y. Farzan, T. Hambye, SPR and S. Pascoli, Phys. Rev. D 77, 043516 (2008)


June 4, 2008


June 4, 2008• Neutrinos are the least detectable

particles of the SM

• From the detection point of view the most conservative assumption is that DM decays only into ν’s : χ → νν

• Flux proportional to the inverse of the DM lifetime and ρDM

• For E ~ 100 MeV – 100 TeV the main background: atmospheric neutrino flux

• Compare potential signal with the well known and measured background: set lower bound on the DM lifetime


June 4, 2008 Signal

dksc JR

dE

dN

mdE

d

0

1

4

Experiment Particle Physics Astrophysics


June 4, 2008 Field of View

Neutrino Spectrum: Flavor democracy

Average of the Line of Sight Integration of ρ

cos12

2/3

2 mE

dE

dN

cos 2)(11 1

cos 00

max

ddrR

Jsc

dk

22 cos2 scsc RRr

cossin 222max scschalo RRR

/

/1

/1)(

s

sscscsc

rr

rR

r

Rr


June 4, 2008

SPR, arXiv:0712.1937to be published in Phys. Lett. B

Model-independent boundfrom CMB observations

K. Ichiki, M. Oguri and K. Takahashi,Phys. Rev. Lett. 93, 071302 (2004)

GeV 10

GeV 1030 E

Eo

GeV 10 30 Eo

4

Using SK data from DSNB search:Detailed analysis of background and energy resolution

New model-independent boundfrom CMB and SN observations

Y. Gong and X. Chen, arXiv:0802.2296


June 4, 2008

Conclusions• Neutrino detectors can test DM properties

• Searches for neutrinos from DM annihilations/decays in celestial bodies could constitute powerful probes of DM properties

• Cherenkov neutrino detectors/telescopes are counting experiments and could only provide limited information

• Future neutrino detectors (MIND, TASD and LArTPC) will have very good energy resolution for 10’s GeV

• Reconstructing the neutrino spectra → information on DM mass, annihilation branching ratios and DM-proton cross section

• Due to small size, only suitable for large spin-dependent cross sections and neutrinos from annihilations in the Sun, but complementary to Neutrino Telescopes (with higher threshold)

• Neutrino detectors can set model-independent bounds on the DM annihilation cross section and on the DM lifetime

• Future detectors (LENA) might be able to detect a signal from DM annihilations/decay


June 4, 2008

When you have eliminated all which is impossible,

then whatever remains, however improbable,

must be the truth

Sherlock Holmes

The world is full of obvious things which nobody by any chance ever observes

testing dark matter with neutrino detectors

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